the impact toughness of Q450NQR1 can be effectively improved by adjusting its chemical composition, with targeted modifications to key alloy elements that directly influence the material's toughness.
Ni is a core element for enhancing low-temperature toughness. Q450NQR1's standard (GB/T 4171-2008) allows Ni content up to 0.65% (optional). Raising Ni within this range refines the steel's microstructure, reduces brittle phase formation, and improves the material's ability to absorb energy during impact-critical for resisting fracture in cold environments (-40℃ or lower).
While Q450NQR1 relies on P (0.07–0.15%) for corrosion resistance, excessive P can cause grain boundary segregation and brittleness. Optimizing P to the lower end of its standard range (e.g., 0.07–0.10%) balances corrosion resistance and toughness. Additionally, minimizing S (to <=0.035%, as per the standard) reduces brittle MnS inclusions, which are weak points that trigger impact fracture.
Properly increasing Mn (within the standard 1.00–1.60% range) enhances solid solution strengthening without sacrificing toughness. Controlling Si to 0.15–0.50% (standard range) avoids excessive Si-induced brittleness, ensuring the steel maintains ductility under impact loads.
